1. Field of the Invention
The invention relates to electric motors used in ceiling fans. More particularly, the present invention relates to methods and apparatus for balancing ceiling fan electric rotary motors.
2. Description of the Related Art
Rotary ceiling fans are well known in the art. A problem frequently occuring in an installed ceiling fan is balance. The blades of the fan, or the internal elements of the fan, may not be properly aligned or the weight may not be evenly distributed, thereby causing the fan to gyrate about its axis. Such gyration or wobbling causes uneven airflow, occasionally unpleasant noise, and may cause excessive wear of the fans and its components.
Exemplary of ceiling fans of the prior art are those disclosed in the following U.S. Patents:
U.S. Pat. No. 4,900,236 discloses a ceiling fan including a rotatable assembly to which the fan blades are attached and a stationary assembly capable of being connected to a suspension device. These assemblies have a common centerline, and the rotary assembly includes the rotor and the stationary assembly, the stator, located concentrically inside the rotor, of an electric motor. The rotatable assembly is mounted rotatable relative to the stationary assembly by means of a tubular member extending coaxially with the centerline and a shaft located therewithin. Two bearings are located at a distance one above the other and are mounted between the shaft and the tubular member, at least one of which bearings is a roller bearing. The other one of the two bearings is a journal bearing.
U.S. Pat. No. 4,720,241 discloses a spinner-type electrical ceiling fan having a three part housing which includes a top plate, a central annular band and a bottom plate. The top and bottom plates have depressed, bearing-receiving hubs disposed therein at a central location. An iron armature is secured to the top and bottom plates, with the central annular band snapped into position between the top and bottom plates and around the periphery of the iron armature.
Exemplary of balancing devices of the prior art for rotary devices are those disclosed in the following U.S. Patents:
U.S. Pat. No. 4,674,356 discloses a dynamic rotational counterbalance structure including a discoid balance body having a groove or race formed in an outer circumferential surface of the body. A plurality of movable weights such as spherical weights are positioned in the groove along with a lubricating and noise damping fluid. The groove is closed by an outer circumferential band. At least two of the balance structures are affixed coaxially on a rotatable member to be balanced. During rotation of the member so balanced, the weights shift circumferentially to offset unbalancing forces which influence the rotating member.
U.S. Pat. No. 4,388,841 discloses a load balancing device for rotation apparatus such as washing machines and vehicle tires. In one embodiment the present invention includes an inner conduit defining an interior raceway which contains a high density fluid mass which shifts to oppose load imbalances. Universal mounting brackets are provided attached to the balancing ring to the rotating structure. The attachment brackets are slidable along the ring and adjustable and adapted for securement in various arrangements. In other embodiments the attachment brackets are adapted to accommodate various wheel configurations and bolt spacings for vehicles.
U.S. Pat. No. 3,733,923 discloses an economical automatic balancer for rotating masses characterized by a circular rigid self-sustaining race formed of a precision bent metallic tube having its ends welded together and having a substantially uniform internal diameter so as to define a smooth raceway for spherical counterweights; a plurality of counterweights and a lubricating and damping fluid movably disposed within the race; and a device for rigidly connecting the race with the rotating mass such that the spherical counterweights and a lubricating and damping fluid movably disposed within the race; and a device for rigidly connecting the race with the rotating mass such that the spherical counterweights will align themselves within the race so as to compensate for dynamic unbalance thereof. The use of the precision bent metallic tube effects an automatic balancer that is advantageous over similar prior art balancer, is easily installed in a wide variety of applications, yet is much more economical in its total cost that the prior art balancers.
U.S. Pat. No. 3,339,429 discloses a dynamic balancing system for rotating shafts which includes a clamp for connection around the shaft including a pair of clamp halves generally V-shaped and each having a pair of serrated faces for engaging a cylindrical shaft at two circumferentially-spaced points, the faces having a concave radius of curvature at least greater than the radius of curvature of the shaft and being correspondingly formed with respect to a line bisecting the angle between he faces whereby each clamp half with be automatically centered on cylindrical shafts of different diameters, a plurality or arms connected to the clamp and extending from the shaft at circumferentially-spaced points, and a dynamic balancing ring connected to the arms for disposition concentrically about the shaft.
U.S. Pat. No. 3,321,997 discloses a load equalizer in a vertical spin tub automatic washing machine including a carrier member encircling and secured to rotate with the spin tub, mass members retained by the carrier member peripherally translatable thereto and compressible, and countervailing separator members disposed between mass members for urging the mass members apart.
U.S. Pat. No. 3,282,127 discloses a balancer unit for shafts and other rotarily driven elements having a heavy side and a light side, the balancer unit including weighty balls and a device defining a circumferential ball-receiving and confining path about the axis of the shaft or other driven elements; the balls occupying substantially less than the circumference of the path; the improvement including an annular inner wall-providing but outwardly open ball carrier concentrically and fixedly mounted on the shaft, the inner wall of the carrier providing an outwardly extending circumferential flange defining the outer margin of the ball path, a removable closure secured to the open outer portion of the carrier, a shaft-surrounding weighty annular member in the carrier and having an internal diameter greater than the shaft diameter, a circumferentially arranged yielding device interposed between the shaft and the inner periphery of the annular weighty member to floatingly support the latter in concentric relationship with the shaft when the latter is in motion with the balls in operative shaft balancing position at the "light side" of the latter or when the shaft is stationary, a circumferential series of radially shiftable ball-engageable elements in the carrier and actuated outwardly by a yielding device to normally engage balls in the ball path, a cooperating device provided by annular weighty member and the ball engageable elements for moving inwardly those of the latter remotely located with reference to the direction of movement of the weighty member under centrifugal shift-rotation-induced action so long as the shaft is out of balance.
U.S. Pat. No. 2,836,083 discloses a balancing ring system for a rotatable container mounted on a vertical axis and adapted to hold articles to be rotated with the container, a closed annular duct carried by the container concentric to the geometric axis of the container, a thixotropic substance partially filling the duct and remaining immobile below the critical speed of the container, and a device for rotating the container above the critical speed to flow the substance within the duct and minimize possible unbalanced conditions resulting from the presence of the articles within the container.
U.S. Pat. No. 2,525,781 discloses balancing of rotatable bodies including placing one or more hollow rings partially filled with liquid around the basket. The ring may contain any desirable liquid but it is preferred to use a liquid having a higher density than water, such as a saturated solution of potassium carbonate. Preferably the height(axial dimension) of the ring is at least several times its thickness(radial dimension) for most efficient balancing action.
U.S. Pat. No. 331,450 discloses a centrifugal rotating machine having hollow rings therearound filled with liquid or with balls, or a combination of liquid and balls, or flexible rings therearound formed by endless chains or ropes, to establish equilibrium of the rotating centrifugal machine.